1. Field of the Invention
This invention relates generally to a hydraulic circuit and, more particularly, to an apparatus for regulating or limiting the flow rate in an oil cooler of an automatic transmission.
2. Description of the Prior Art
The required rate of flow of lubricant in an automatic transmission varies with its duty cycle. Lubrication flow rate in automatic transmissions can be controlled using several methods including constant pressure regulator supply, a fixed orifice, priority feed from main transmission pressure regulator, dependant feed from a torque converter or other fluid sources, and variations or combinations of theses methods. Most lubrication schemes for automatic transmissions use a resultant flow rate for all operating conditions. The resultant flow rate requires that lubrication oil in excess of current operating requirements be directed into the transmission components, thereby creating windage losses due to oil shearing in the transmission.
A need exists in the industry for a technique to regulate the flow rate of lubricant in a transmission oil cooler such that it varies with the duty cycle, i.e., the flow rate is high when the magnitude of the load on the transmission is large and the flow rate is relatively low when the magnitude of power being transmitted is low.